This work describes the design of high gain, U-slot antennas for RFID 915 MHz (902 – 928 MHz) applications. Four types of antenna were designed, optimized and evaluated – a circular, U-slotted antenna, a rectangular U-slotted antenna, and two 2x1 arrays. All structures are fed using the co-planar waveguide (CPW) feed. Several miniaturization and gain enhancement techniques such as folding, bending and alternative feeding were applied in the course of achieving the required compactness and radiation characteristics. After investigation, a rectangular, single element U-slot antenna was proposed as the most suitable for this application, considering that it provides a reasonable gain, sufficient bandwidth and compactness.